The present invention provides a method for producing fatty acids from their corresponding alkali metal or alkaline earth metal "salts" or soaps.
When it is attempted to prepare a C.sub.4 - C.sub.30 alkyl carboxylic acid from exemplarily its sodium soap by simple acidification in aqueous medium with a strong acid, several kinds of difficulties are encountered. In order to have both soap and the strong acid in solution, extreme dilutions with impractical amounts of water must be used. Furthermore, phase separation of the fatty acid is not clear-cut and is often fraught with undesirable emulsification.
In particular, these technical problems complicate the exploitation of the well-known OXO process as a means toward producing fatty acids. The literature has described the preparation of soaps by first hydroformylating olefins, followed by alkaline fusion of the resultant oxygenated products, such as alcohols, aldehydes, esters, ethers and high-boiling polymerized substances. The preparation of corresponding fatty acids from these soaps is disclosed, for example in French Pat. Nos. 1,277,098 and 2,080,398.
The disclosed procedures for the acidification of soaps have numerous disadvantages, particularly as a result of the poor solubility of the solid soaps in water, generally of the order of only about 10 to 15%, which requires the use of large volumes of water, about 7 to 10 liters of water per kilogram of soap, which in turn requires correspondingly voluminous equipment and presents a problem in discharging the spent water.
In order to make the soap dissolve more rapidly in water, it is furthermore necessary to submit the solid soap to a preliminary comminution into powder or flakes. Another disadvantage cannot be neglected from a practical point of view is the large amount of foaming which takes place in the course of dissolving the soaps in water with agitation.